1. Cardiology Department, Royal Brompton Hospital , Sydney Street, London SW3 6NP, UK
2. Department of Adult Intensive Care, Royal Brompton Hospital , Sydney Street, London SW3 6NP, UK
3. Guy's and St Thomas' NHS Foundation Trust, Lambeth Palace Road , London SE1 7EH, UK
4. Department of Imaging Sciences and Biomedical Engineering, King's College London , London SE1 7EH, UK